If C and C++ give the best performance, why do we still code in other languages?

This is "old-time" thinking. Computers today are about a powerful as the supercomputers of just 15 years ago when people really cared about CPU performance. Today, the most important factor is the ability of a programmer to create error-free code that will operate the same on many different platforms. The only exceptions to this are production platforms where the ability to execute in close to real-time is the object. Even there, the production code is probably not C or C++ or C##, but most often Cobol for business applications, and Fortran for scientific applications. I always bet on the side of Moore's Law that CPU performance and memory size will double every year. It's been true since Gordon Moore and others founded Intel, and even though the mechanisms have changed, it still appears to hold today.

If a chainsaw can cut down a tree, why do we still have hammers?  Performance isn't the only factor when choosing a development language, you also have to consider time and cost.

Development time is more important than the computing resources these days. C/C++ give full access to developers which becomes difficult to handle sometimes so other "safe" languages like C#, Java etc. are preferred. Another reason might be the availability of more advanced tools and IDEs available for high level languages than we have for C/C++.

It all depends on the type of requirement you have in front. I write and have written code in C/C++, Java, C# .NET, Ruby, JS, HTML etc. The choice between all of these languages is totally dependent on the requirement of what is to be developed. Suppose, I need to write a network driver which will run on TCP/UDP sockets and interact with the device, of course I will choose C/C++ why because no other language will provide me low level support to access system and OS resources. The code written in C/C++ will automatically be faster as there are no wrappers like JAVA, .Net etc and the driver does not need to present UI to user which can be coded independently in another technology. Now if I have the requirement to design web pages I would choose JS and HTML, why because all browser supports the code written them in a very efficient way, plus this technology was developed for rendering web pages so it provides me various tool kits and techniques which will make me code faster with improved performance. If the same work has to be done in C/C++, how would I have done it, I would have to write my own wrappers over C/C++ which will provide me various UI controls, various libraries which will automatically manage my code as C/C++ does not provide effective and automatic memory management and resource management techniques, this would we a great pain area. So when there is already the work done in HTML,JS which if we see is a wrapper over wrappers over the low level technologies like C/C++ why would one go and create his own new HTML and JS. Same applies to requirement when I need to create a window UI or a web service I will choose between JAVA, .NET etc/ depending upon on other dependencies.

It's simply not true. Aside from the basic "Hello World" or primitive loop scenarios, any application's performance has much more to do with design and the developer than then choice of programming language.

Nothing is a best approach for all requirements. Everything has its pros and con's. There are  hundreds reason to opt php in place of c and c++ for such cases like for web applications, for low costing purpose,for easily availability of resources etc.

What everyone said, PLUS: There's stuff you CAN'T DO in C/C++. That's right. You're not alone in this world. People wrote browsers, so you need to know HTML and JS. People wrote web servers and infrastructure, so you need to know PHP (Or whatever server scripting etc.). Etc, etc etc.

If racing cars are the most performant automobile around, why do we still drive in Priuses and SUVs? The answer is: the right tool for the right job.

C/C++ compared with (as in the OP) Perl, Ruby, PHP, including Java which are interpreted/or similar, languages has no comparison. I've stuck with C and C++ because I 'can' get things done with them. One of the reasons C/C++ is still popular is because there are so many older programmers out there now that act as mentors and offer their time to give both help and advice. Java raised it's popularity because it was easier to learn than C++ but when it comes to bottle necking in your code, you just cannot beat a low level language and raw speed. I won't be mentioning assembly coding here. There are many good web programmers out there but how many of them (apart from those that work at google) actually use C++? When it comes to web design, nothing beats a team of one who is a good programmer and another who is good at networking. With the advent of devices such as the raspberry pi and other such devices being introduced into school, we might soon see another breed of good programmers in the near future. During the 80's was a big boon in programming skills from all over the world. Anyway, that's my rant and its late.